UNIVERSITY CHALLENGE. I’m on the UCL alumni team with Jeremy Bowen, Jessica Curry and Jane Dacre. We beat Leicester in round one and tonight (4 January) we take on Reading (where I got my undergraduate degree!) in the semi-final. BBC Two at 7:30.

Social epidemiology never generates straightforward policy prescriptions. Even if we know something makes us live longer, we still have to ask if it is right to promote it. It might be that many features of more traditional societies, including religiosity and tight social relations, are good for health. But it does not follow that we can or should try to turn back the clock. That is a philosophical and political question, not one for epidemiology.

To rebuild belief in the power and value of truth, we can’t dodge its complexity. Truths can be and often are difficult to understand, discover, explain, verify. They are also disturbingly easy to hide, distort, abuse or twist. Often we cannot claim with any certainty to know the truth. We need to take stock of the various kinds of real and supposed truths out there and understand how to test their authenticity.